1. Field of the Invention
The present invention relates generally to medical devices and methods. More particularly, the present invention relates to methods for inhibiting and treating the infection of implanted devices and to modified devices which facilitate such methods.
Subcutaneously and transcutaneously implanted devices are utilized for a wide variety of purposes. Heart pacemakers have become commonplace. Transvascular catheters are used for a variety of purposes, including hemodialysis access, drug infusion, and the like. Of particular interest to the present invention, subcutaneously and transcutaneously implanted ports and catheters have been proposed for both drug infusion and hemodialysis access. All such implanted devices are subject to infection. Subcutaneously implanted ports which are periodically accessed by needles and other percutaneously introduced devices are particularly subject to infections introduced by the access device.
Most infections of subcutaneously implanted ports begin as bacteria from the skin are carried into the tissue tract and port by the needle penetration. An infection can then grow internal to the port or within the tissue xe2x80x9cpocketxe2x80x9d which surrounds the port. A tissue pocket will form when the exterior surface of the port or other device is impermeable to tissue in-growth, e.g. where the surface is hard and composed of a metal, such as stainless steel, titanium, plastic, or the like. Infection can enter the space between the external surface of the device and the opposed tissue surface and can spread throughout the tissue pocket and sometimes into adjacent spaces, e.g. the space around a cannula attached to the port and leading to a blood vessel or other body lumen. While initially localized, the infection can become systemic and place the patient at significant risk.
Heretofore, infections of subcutaneously implanted devices have usually been treated by the systemic administration of antibiotics to the patient after infection has become established. Often, the implanted device must also be removed and replaced, subjecting the patient to additional trauma and leaving the patient without benefit of the device for the time it takes to clear the infection and replace the device. Moreover, the need to administer antibiotics periodically to patients is expensive and patients who suffer from repeated infections often become resistant to particular antibiotics.
As an alternative to antibiotic treatment and/or device removal, U.S. Pat. No. 5,263,930 proposes to provide a disinfectant reservoir in an implantable vascular access port. The reservoir includes a septum to permit periodic replenishment with a suitable anti-microbial agent. Agent introduced into the reservoir flows into an access lumen through the device. Catheters and other devices inserted into the access lumen become coated with the anti-microbial agent to provide a barrier against infection along the percutaneous access route. In particular, the design is intended to prevent infection of the bloodstream. While potentially beneficial, the provision of a static volume of anti-microbial agent within a reservoir does not provide flushing and active decontamination of the tissue pocket surrounding the implanted port. Thus, should bacteria be introduced into the tissue pocket, it is unlikely that the anti-microbial agent would be effective to inhibit infection.
For these reasons, it would be desirable to provide improved methods and devices for inhibiting bacterial and other infections in subcutaneously implanted devices. It would be particularly desirable to provide methods and devices for active flushing of the implanted device as well as the tissue pockets and regions surrounding the device in order to maximize the disinfection process. It would be particularly useful if such methods and devices were applicable not only to implantable ports but also to other subcutaneously and transcutaneously implanted devices. At least some of these objectives will be met by the present invention as described hereinafter.
2. Description of the Background Art
U.S. Pat. No. 5,263,930 has been described above. A transcutaneous vascular access port sold under the tradename HEMASITE(copyright) II by Renal Systems, Inc., Minneapolis, Minn., includes an above-skin reservoir for a bactericide, as described in a brochure entitled Vascular Access System copyrighted by the manufacturer in 1984. Catheters having bacteriocidal coatings and release capabilities are described in U.S. Pat. Nos. 5,599,321; 5,591,145; 5,482,740; 5,261,896; 5,236,422; 5,004,455; 4,959,054; 4,767,411; and 4,579,554.
The present invention provides methods and improved apparatus systems, and kits for inhibiting and/or treating infection of subcutaneously and transcutaneously implanted devices. As used hereinafter, the phrase xe2x80x9cinhibiting infectionxe2x80x9d will refer to both prophylactic treatment to avoid infection and therapeutic treatment to eliminate an established infection. The methods and apparatus are particularly applicable to disinfection of implanted vascular and other access ports which are at substantial risk of infection through repeated percutaneous access via needles, access cannulas, stylets, and the like. The present invention, however, will also be useful with a variety of other subcutaneously implanted devices, including pacemakers, catheters, prosthetic joints, defibrillators, implantable infusion pumps, and the like.
The present invention relies on percutaneous injection of an anti-microbial agent in an amount sufficient to infuse a region within and/or surrounding the device. For prophylactic treatment, the anti-microbial agent may be any one of a variety of conventional bactericidal, fungicidal, virucidal, or other disinfecting agents, typically being selected from the group consisting of sodium hypochlorite, calcium hypochlorite, sodium oxychlorosone, alcohols, aldehydes, halides, providone iodine, peroxides, and the like. For treatment of established infection, the anti-microbial agent will usually be the same, and the treatment may be supplemented with the systemic administration of an antibiotic, such as penicillin, vancomycin, and the like. The anti-microbial agent will flowable so that it can be percutaneously introduced to the implanted device, usually being in the form of a liquid, although it could also be a flowable gel, and will usually be injected at a volume in the range from about 0.05 ml to 50 ml, often from 0.1 ml to 25 ml, more often from 0.5 ml to 25 ml, and typically from 0.5 ml to 10 ml. Injection will conveniently be effected using a needle which can be penetrated directly through the skin, typically in combination with a conventional syringe.
The extent and nature of the region which is irrigated or flushed will depend greatly on the geometry and type of the implanted device. For implanted devices having internal spaces, such as implanted ports having apertures for receiving percutaneous access tubes, it will usually be desirable to infuse and flush at least the internal space with the anti-microbial agent. Preferably, at least a portion of any tissue pocket surrounding the implanted device will also be infused and flushed with the anti-microbial agent. More preferably, a sufficient amount of the anti-microbial agent will be introduced to flush outwardly through the access tissue tract which is used to introduce the flushing needle and/or to subsequently introduce an access tube. In particular, the present invention is able to disinfect the tissue tract used for subsequently introducing an access tube and to leave a sufficient amount of anti-microbial agent to disinfect any bacteria which are on the access tube when it is later introduced.
For transcutaneously implanted device, i.e. devices which pass through an access site in the patient""s skin (such as transcutaneous catheters), the anti-microbial agent is preferably introduced at a site just proximal to an infection barrier, such as an infection-inhibiting cuff on the catheter. In this way, the anti-microbial agent can be flushed outwardly back through the tissue track surrounding the catheter or other device and through the access site in the skin. The ability to both disinfect and flush the bacteria from the tissue region surrounding the transcutaneous catheter or other transcutaneous device is particularly beneficial in inhibiting infection.
In a preferred aspect of the method of the present invention, the subcutaneously implanted device is a port which is connected to a blood vessel, other body lumen or cavity, or solid tissue target site, usually using a cannula. The port has an aperture for receiving a percutaneous access tube, e.g. a needle. The anti-microbial agent is injected directly into the aperture to both flush the aperture and any internal volume surrounding or in fluid communication with the aperture, with excess anti-microbial agent being flushed from the aperture to infuse a region or space surrounding the port within the tissue pocket in which the port has been implanted. Usually, the port will be valved or have a septum to isolate the access aperture from that portion of the port which is connected to the cannula and/or the blood vessel or body lumen. Thus, flushing of the port with the anti-microbial agent can be performed without introduction of the agent beyond the valve, i.e. into the blood vessel or other target site. The needle used to flush the access port will be introduced in a manner which does not open the valve structure or septum, thus maintaining isolation. The needle used to introduced the anti-microbial agent, however, will usually be introduced through the same site or tissue tract as the primary access tube, thus reducing patient trauma. The disinfecting needle will usually be smaller than the access tube, even further reducing patient trauma.
The methods of the present invention are also useful for disinfecting and inhibiting infection with ports and other subcutaneously implanted devices which do not have open access apertures. In such cases, it will usually be unnecessary to disinfect internal portions of the device, and the disinfecting needle can be contacted directly against an external surface of the device in order to infuse the anti-microbial agent within the tissue pocket surrounding the device. Optionally, the needle may be contacted against a specially configured target site on the device, e.g. a well or other region on the device composed of or lined with a relatively hard material that can withstand repeated contact with the disinfecting needle. The well or other target can be located by the treating professional, e.g. by manually feeling it through the skin, and will be positioned to permit the anti-microbial agent to infuse freely about the exterior of the device at the interface between the device and the tissue. In some cases, it may be desirable to connect the well to channels or other surface features which permit the anti-microbial agent to suffuse freely around the periphery of the device.
In yet another embodiment, the methods may be used to disinfect transcutaneously implanted devices, such as catheters. In such cases, the disinfectant is infused into the tissue pocket formed about the device, usually by injection into tissue through a location adjacent to device penetration site. As with previous embodiments, the disinfectant is able to suffuse and flush the tissue pocket, and the excess disinfectant will flow outward around the device onto the patient""s skin, to assure thorough disinfection.
In an alternative aspect, a method according to the present invention for detecting infection of an implanted device comprises injecting a flowable material through a tissue tract into a region within or surrounding at least a portion of the device. The flowable material will usually be an anti-microbial disinfectant material as described previously, but could also be saline, water, or other sterile material which can flow into the region, flush the region, and carry visible products of infection back outwardly through the tissue tract. At least a portion of the injected material will flow outwardly back through the tissue tract in order to transport visible material resulting from infection back to the surface of the skin. By then observing that portion of the injected material which flows outwardly from the tissue tract, a determination can be whether an infection exists. Usually, the material which is initially injected will be relatively clear. If the material which is flushed from the tissue tract is milky and contains considerable debris, it is likely that an infection has become established. In that case, the infection may be treated by irrigating the device with a large volume of an anti-microbial material according to the present invention. Alternatively or additionally, the patient could be treated with systemic antibiotics or in other conventional ways.
The present invention further provides improved implantable devices of the type which include a housing implanted within a subcutaneous tissue pocket. The improvements comprise a non-penetrable target site on the housing for receiving a disinfecting needle to permit delivery of an anti-microbial agent as described above. Preferably, the non-penetrable target site is composed of or lined with a metal or other material which is sufficiently hard to withstand repeated engagement by the disinfecting needle. Suitable materials include metals, such as titanium, vanadium, stainless steel (particularly 316L), as well as implant grade plastics and ceramics. The well may have a circular geometry, an annular geometry, or may be connected to a network of channels or wells which facilitate distribution of the anti-microbial agent about the device implanted within the tissue pocket.
The present invention still further provides systems for disinfecting and accessing an implanted port. The systems will comprise a needle adapted to deliver a flowable anti-microbial agent to the implanted port, typically according to the methods described above. Usually, the needle will be attached to a syringe, and the syringe will usually be pre-filled with a suitable anti-microbial agent. The types and amounts of anti-microbial agent will be generally as described above. The system will still further include an access tube suitable for percutaneously coupling to the implanted port to deliver or receive a flowable material therefrom, e.g. in the case of ports connected to the vasculature. In other instances, the flowable material may be dialysate used in peritoneal dialysis. The access tube may also be in the form of a needle, and will usually be connected to a catheter having a hub or other structure at its proximal end for connecting to external equipment. Such systems may further comprise instructions for delivering the anti-microbial agent to the implanted device through the needle and thereafter for connecting the access tube to the implanted port after it has been disinfected. optionally, the systems may be packaged together in conventional packages, such as pouches, trays, tubes, boxes or the like.
The present invention still further comprises kits including one or more of the apparatus and system components described above together with instructions for use according to any of the methods described above. For example, a kit according to the present invention may comprise any implantable device, such as an implantable port intended for percutaneous access via an access tube as described above, together with instructions for use for inhibiting infection of the device by introducing an anti-microbial agent to the device after it has been implanted. A second exemplary kit might comprise a container holding a volume of the flowable anti-microbial agent, e.g. a syringe holding the flowable anti-microbial agent having a needle for introducing the agent through the percutaneous tissue tract. The container or syringe would be combined in a kit with instructions for use setting forth methods for introducing the anti-microbial material from the container through a tissue tract or injection site to an implanted device. A third exemplary kit would include the container and instructions for use, as just described, further in combination with an access tube intended for accessing an implantable port. A fourth exemplary kit would include the access tube together with instructions for use for introducing an anti-microbial material through a tissue tract prior to introducing the access tube through the same tissue tract. All of the above kits will typically be placed together in a common package, such as a pouch, box, tube, tray, or the like. More usually, all kit components will be sterilized within the packaging and will be available for immediate use after the package is opened.